Characterization of mitochondria isolated from the freezing-tolerant larvae of the goldenrod gall fly (Eurosta solidaginis): substrate preferences, salt effects, and pH effects on warm- and cold-acclimated animals

Abstract

The mitochondria of the freezing-tolerant larvae of the goldenrod gall fly (Eurosta solidaginis) have been isolated and characterized. Proline is the preferred substrate of mitochondria from both warm- and cold-acclimated animals based on state 3 rates. Lipid is used as a substrate by warm- and cold-acclimated mitochondria assayed at 20 °C, but not by the mitochondria from cold-acclimated animals assayed at 1 °C. Cold-acclimated mitochondria assayed at 1 °C have a higher and broader optimal range of salt concentration for the oxidation of proline based on the respiratory control ratio (RCR) than those from warm-acclimated animals oxidizing the same substrate at 20 °C. The optimal pH for warm-acclimated mitochondria oxidizing proline at 20 °C is low (6.2) based on the RCR, but rises to pH 7.0 in cold-acclimated animals at 1 °C. It is suggested that the broad optimal salt concentration in the cold-acclimated animals and the very low optimal pH in warm-acclimated animals are adaptations for survival in this freezing-tolerant larva.